...what makes you question if they were off a newer truck?...
Just a guess from the picture and what I've seen on other trucks, no concrete reason and no way to explain it..
The first record I show of an AR mount is 1949. ...There's also an old style AR and a new style AR shown in a 1953 K-H catalog. Yours look old style.
There's your real answer, about 49-52 or so.
What's the pilot diameter on your 36 hubs?
The new wheels you found are for 4.75" hubs.
Some of the really old Chevy trucks with the same bolt pattern have even smaller hubs and the center hole in the wheel is smaller to match.
Grigg